Fluid flow in tubing

ABSTRACT

There is disclosed a method for configuring or reconfiguring branches in tubing in which the axes of at least two components of the branched structure are arranged askew.

[0001] This invention relates to fluid flow in tubes, particularly, butby no means essentially, blood flow tubing and other tubing carryingfluids essential to life.

[0002] In WO 00/38591 is described tubing adapted to induce helical flowin such fashion as to eliminate or reduce turbulence and/or eliminate orreduce dead flow regions in the tubing. The tubing has internal helicalgrooving or ridging or other measures designed having regard to thedimensions of the tubing and the density, viscosity and velocity of theflow. Particular problems arise in connection with branched tubing, inwhich fluid flows from a main trunk into two or more branches, or,alternatively, flows from two or more branches into a main trunk.Certain blood carrying vessels as well as air passages in human oranimal bodies experience such branching. When such branched tubing isrepaired or replaced, as in vascular grafting, heart bypasses and soforth, it may be advantageous to reconfigure such tubing to improvefluid flow at such branch. One way of reconfiguring the tubing would beto introduce helical ridging or grooving in the manner taught in WO00/38591, but this is not always possible.

[0003] In accordance with the present invention, there is provided amethod of configuring or reconfiguring branches in tubing in which theaxes of at least two components of the branched structure are neitherintersecting nor parallel and in which at least one of the components ofthe branched structure itself has internal helical ridging and/orgrooving adapted to reduce or eliminate turbulence and/or dead regionsin flow through the tubing.

[0004] The axis of a circular section tube is, of course, well defined.More generally, the axis of a non-circular section tube is taken forpresent purposes to be the locus of the centres of gravity of adjacentlengthwise slices through the lumen of the tube. An axis may, then, notbe a straight line, as the branch may be curved.

[0005] Typically, the internal helical ridging and/or grooving isadapted to cooperate with the skew arrangement of any components of thebranched structure—if, for example, the skew arrangement is intended toproduce a clockwise rotary component in the flow, viewed along thedirection of flow, then the internal helical configuration of at leastone component of the branched structure may also be arranged to producea clockwise component

[0006] To avoid the creation of incidental turbulence, it may bearranged that internal surfaces of the branched structure have no sharpedges.

[0007] An example of a branched tubular configuration according to theinvention will now be described with reference to the accompanyingdrawings, in which:

[0008]FIG. 1 is a lengthwise section through a first embodiment;

[0009]FIG. 2 is a non-sectional view on Arrow 2 of FIG. 1;

[0010]FIG. 3 is a non-sectional view on Arrow 3 of FIG. 1; and

[0011]FIG. 4 is a lengthwise section through a second embodiment.

[0012] The drawings illustrate methods for configuring branched tubularstructures 11, each comprising a main trunk portion and two branches.

[0013] FIGS. 1 to 4 illustrate a structure in which fluid flow is intothe main trunk 12 from two branches 13. The offset arrangement of thebranches 13 causes rotational flow in the main trunk 12, as indicated bythe flow arrows. In addition, the main trunk 12 includes internalhelical ridging 15 that is adapted to cooperate with the skewarrangement of the branches 13 to aid production of rotary flow in themain trunk 12.

[0014] As the general idea is to reduce or eliminate turbulence and/ordead spaces, the branched structure will need to be configured as to thedimensions of the tubes, especially the relative flow capacities of thetrunk 12 and branches 13, the viscosity and density of the fluid flowingin them and the flow velocities, to optimise the flow characteristics.It may be that this can all be worked out by computational fluiddynamics, or it may be dealt with on a trial and error basis in which arange of configurations is investigated.

[0015]FIG. 4 illustrates a branched structure in which the fluid isflowing from the main trunk 12 into the branches 13. Here, the flow isprepared in advance of the junction to have a rotational component inthe correct sense by means of internal helical ridging and/or grooving14 in the inner wall of the trunk 12.

[0016] Of course, structures of more complex geometry can becontemplated, for example a trunk dividing into three or more branches,a structure in which two or more branches flow into two or more furtherbranches, and so forth, all of which can be dealt with by offsetting thebranches as above described.

[0017] The invention may have particular relevance in relation to tubingin which body fluids flow, such for example as veins and arteries, forthe avoidance or reduction of tendency to atherosclerosis and theformation of clots that can break away leading to strokes. The design ofartificial vascular grafts and particularly patches for coronary bypasssurgery may benefit from the teachings herein. A particularly importantbranched structure is the respiratory system, and, while surgicalintervention may not bring about structures that were not already inplace, at least the teachings herein may serve to avoid the creation ofstructures which create unwanted turbulence and/or dead spaces in thesystem.

[0018] The invention, however, will find many applications outside ofthe clinical field, in, for example, the design of pipework inmanufacturing plant, in oil delivery pipelines and in air conditioningand central heating systems.

1. A method of configuring or reconfiguring branches in tubing in whichthe axes of at least two components of the branched structure areneither intersecting nor parallel; and in which at least one of thecomponents of the branched structure itself has internal helical ridgingand/or grooving adapted to reduce or eliminate turbulence and/or deadregions in flow through the tubing.
 2. A method according to claim 1, inwhich the said internal helical ridging and/or grooving is adapted toco-operate with the skew arrangement.
 3. A method according to claim 1or claim 2, in which internal surfaces of the branched structure areconfigured or reconfigured to be smooth, with no sharp edges.
 4. Tubingconfigured or reconfigured according to a method according to any one ofclaims 1 to
 3. 5. Tubing according to claim 4, being blood flow tubing.7. Tubing configured or reconfigured according to a method according toclaim
 6. 8. Tubing according to claim 7, being blood flow tubing.
 9. Amethod for configuring or reconfiguring branches in tubing having abranched structure including a main tube component joined to at leasttwo branch tube components at a juncture for flow of fluid through saidcomponents, each of said components having a length and a flow axisextending centrally through a lumen of the component, comprising thestep of configuring or reconfiguring said branch components to disposesaid branch component axes in a skewed orientation at said juncture andproviding at least one of said components of said branched structurewith an internal surface helical configuration arranged to reduce oreliminate turbulence and/or dead regions in fluid flow through saidcomponents.
 10. A method according to claim 9, wherein said helicalconfiguration is arranged to cooperate with fluid flow resulting fromsaid skewed orientation of said axes.
 11. A method according to claim 9,wherein said components have internal surfaces configured orreconfigured to be smooth and free of sharp edges.
 12. Tubing configuredor reconfigured in accordance with the method of any one of claim 9, 10or
 11. 13. Tubing according to claim 12, wherein said fluid is blood.